The human body functions through a number of interdependent physiological systems controlled through various mechanical, electrical, and chemical processes. The metabolic state of the body is constantly changing. For example, as exercise level increases, the body consumes more oxygen and gives off more carbon dioxide. The cardiac and pulmonary systems maintain appropriate blood gas levels by making adjustments that bring more oxygen into the system and dispel more carbon dioxide. The cardiovascular system transports blood gases to and from the body tissues. The respiration system, through the breathing mechanism, performs the function of exchanging these gases with the external environment. Together, the cardiac and respiration systems form a larger anatomical and functional unit denoted the cardiopulmonary system.
Various disorders may affect the cardiovascular, respiratory, and other physiological systems. For example, heart failure is a clinical syndrome that impacts a number of physiological processes. Heart failure is an abnormality of cardiac function that causes cardiac output to fall below a level adequate to meet the metabolic demand of peripheral tissues. Heart failure is usually referred to as congestive heart failure (CHF) due to the accompanying venous and pulmonary congestion. Congestive heart failure may have a variety of underlying causes, including ischemic heart disease (coronary artery disease), hypertension (high blood pressure), and diabetes, among others.
Abnormal breathing patterns often occur in conjunction with congestive heart failure (CHF). A form of disordered breathing is known as periodic breathing (PB). In particular, a form of periodic breathing known as Cheyne-Stokes respiration (CSR) is commonly associated with poor prognosis when diagnosing CHF patients. Some studies have suggested that disordered breathing is related to a higher incidence of cardiac arrhythmia.
External breathing therapy may be prescribed for patients suffering from various types of breathing dysfunction. For example, positive airway pressure devices are often used to treat disordered breathing such as CSR and other types of disordered breathing. The positive airway pressure provided by the device acts as a pneumatic splint keeping the patient's airway open and reducing the severity and/or number of occurrences of disordered breathing events due to airway obstruction.
Effective approaches to monitoring and evaluating cardiac conditions in patients receiving therapy for respiratory disorders is desirable. The present invention fulfills these and other needs, and addresses other deficiencies of prior art implementations and techniques.